1. Field of the Invention
The present invention in general relates to appliance timers and more particularly to the clutch mechanism of such timers.
2. Description of Prior Art
Electromechanical timers have been known as long as automatic appliances. A common form of such a timer includes a motor, a gear train, a camstack driven by the motor and gear train, and switches which are opened and closed by cams on the camstack to operate a programmed sequence of appliance functions. Generally it is desirous in such timers to be able to manually set the camstack to a desired program cycle. During such manual setting the camstack is turned at a much higher rate of speed than it is when driven by the motor and gear train. To enable the camstack to be turned easily and to prevent damage to the motor and gear train, it is desirable to place a friction clutch between the gear train and camstack. For more than two decades, a standard clutch for such purposes has comprised a clutch plate integrally formed with a large gear sandwiched between two dimpled spring washers. See, for example, the clutch disclosed in U.S. Pat. No. 3,500,005 issued to W. R. Brown. The connection between the cam drive shaft and the clutch spring washers is critical in such a timer, and thus these parts are conventionally made of stainless steel and the drive shaft is staked to the spring washers. The steel shaft is a screw machined part and relatively expensive compared to other materials generally used in timers and more difficult to manufacture than other materials. Thus, a timer clutch that is reliable as prior art clutches in combination with a drive shaft that is made of die cast zinc, zinc alloy, or other moldable material which is relatively inexpensive and easily manufactured would be of significant advantage.